换能器阵列的传输线矩阵方法分析

介绍将传输线矩阵方法应用于声光换能器阵列的辐射特性分析，给出了与解析方法一致的数值结果。表明传输线矩阵方法可以用于对声学器件的工作过程进行时域数值模拟。     

Matched absorbing medium techniques for full-wave tlm simulation of microwave and millimeter-wave components

This paper investigates the absorbing layer techniques for three-dimensional transmission-line matrix (3d-tlm) simulations. Applications are the full-wave analysis of structures such as microwave and millimeter-wave circuits open to free space. Two approaches are presented, namely the matched layer (ml) and the perfectly matched layer (pml) technique which is used for general cases. For the ml technique, which is efficient for matching guides operating in a quasi-TEM condition, a comparison of the different tlm condensed node is carried out. Concerning the more general case of the pml technique, the theoretical development of a new general three-dimensional (3d) tlm condensed cell is presented. Results pertaining to the characterization of planar circuits are compared with other solutions or measurements. It is found that a proposed unified approach, which includes the tlm simulation for matched layer media, yields very good performance in terms of the absorbing boundary condition (abc).     

An Equivalence Principle for Nonuniform Transmission-Line Directional Couplers

The analysis of transmission-line directional couplers is formulated in terms of a pair of first-order matrix differential equations. It is shown that for every nonuniform directional coupler that is electrically symmetric, there exists an equivalent pair of dual nonuniform transmission lines. It is also shown that a matched, transmission-line directional coupler having an absolutely continuous characteristic impedance matrix must be symmetric. Restrictions on the terminating impedances and the implications of these restrictions on the realizability of transmission-line couplers are investigated. Finally, the tapered-line magic T is treated as an example.     

用光学传输矩阵模拟光致抗蚀剂中的驻波效应

抗蚀剂曝光的模拟与光刻系统空间像模拟紧密相连 ,一般是用标量衍射方法在特殊几何形状的光源分布和特殊掩摸结构的条件下计算的 ,实质是一定边界条件和初始条件下 Maxwell方程组的求解。驻波是曝光中的寄生效应 ,是光线垂直入射到不同的平行平面介质层之间 ,经多次反射并干涉形成的。驻波的边界条件是平行界面上电磁场矢理的连续。在这种条件下对驻波的描述有 BERNING的多层光学薄膜模型和 MACK的膜层递推解析模型。本文用传统的光学传输矩阵模型来描述 ,建立了简洁有效的迭代算法 ,分析了该算法的收敛性 ,并编制出相应的计算程序 ,给出了计算结果     

纳米金属-介质多层膜的局域场增强及透射特性研究

采用转移矩阵法(TMM)分析了纳米金属-介质多层膜的局域场增强效应及光选择透射特性.当满足波矢匹配条件,金属-介质-金属(MDM)膜中将激发产生体等离激元(BPP),BPP模的阶数与多层膜结构中的介质层数相同.BPP模激发时入射光与金属膜层的自由电子耦合,耦合作用使入射光透过金属层传输,透射率达到最大值,同时介质内的局...     

Decoupled simulation of DC-linked power electronic systems usingtransmission-line links

This paper describes the application of the transmission-line modeling (TLM) method to the decoupled simulation of DC linked power electronic systems. Stiff capacitively or inductively smoothed DC links in power electronic systems can be modeled as two-port transmission-line links using the TLM method. The TLM links enable the circuits connected by the links to be decoupled and simulated as individual circuits, resulting in smaller system matrices, possibility of parallel computation and reduction in computing time. Interaction between these linked circuits can be realised by exchanging the incident pulses at both ends of the transmission-line links. Computer simulations of an AC to DC converter used in a laboratory confirms the simplicity of the TLM decoupled simulation approach     

平坦地条件下移动通信基站天线远场分析

介绍了一种平坦地条件下基站天线远区场分析的理论方法。文章利用射线跟踪法,通过建立适当坐标系进行三维建模,结合电磁散射矩阵关于散射场入射场关系进行理论分析。文中采用最常见的对称天线模拟基站天线,对某900 MHz GSM落地式基站进行电磁环境仿真,对仿真结果进行分析并与实测数据比较,得到结论:在距离基站30 m范围之内,要同等考虑直射信号与地面反射信号对场观察点的场强贡献,在距离＞30 m时,只需考虑天线直射信号对场观察点的场强贡献。     

1维光子晶体中TM波的传输公式及其辨析

为了得到1维光子晶体中TM波的传输公式,采用传输矩阵的方法和电磁波的边界条件,推导出TM波在介质层中的特征矩阵及其反射系数和透射系数公式。结果表明,用TE波反射系数和透射系数公式做代换的方法不能得到正确的TM波的反射系数和透射系数公式;对推导出TM波的反射系数和透射系数公式进行了分析,由TM波的反射系数和透射系数公式得出的光强透射率和反射率满足能量守恒;并且推出的TM波反射系数公式不仅能够反映反射波与入射波的数量关系,且能够反映反射波与入射波的位相关系。这些结果对研究1维光子晶体中TM波的传输性质是有帮助的。     

Literal solutions for the time-domain response of a two-conductortransmission line excited by an incident electromagnetic field

Analytical solutions of the transmission line equations for a lossless, two-conductor transmission-line with incident electromagnetic field illumination are obtained. The equations for the terminal voltages are in terms of symbols, rather than numerical values. This form of the solution gives insight into the various factors that contribute to the overall, time-domain response waveshape that would be obscured in a numerical solution. The results are specialized to uniform plane wave illumination and to electrically short lines     

利用小型化频率选择表面实现宽带电磁透明

为了实现微波宽带高透明性材料,采用了小型化频率选择表面的方法,设计了一种由一层容性贴片和一层S形感性网栅构成的电磁透明材料,结果表明,这种电磁透明材料-1 dB相对带宽可达99.4%,实验结果与仿真结果吻合。同时,斜入射实验结果显示,该结构在横电波和横磁波偏振入射波40°角入射条件下仍具有较好的角度稳定性。     

Frequency-selective transmission by a leaky parallel-plate-like waveguide

The phenomena of high frequency-selective transmission of a plane wave by a dielectric two-dimensional (2-D) periodic waveguide, comprising a uniform dielectric layer sandwiched by two finite thickness 2-D periodic structures served as the waveguide wall is described. This structure is termed a leaky parallel-plate-like waveguide because the waveguide walls are not perfect reflection mirrors. The scattering characteristics and dispersion relation, including the phase and attenuation constants, of the 2-D periodic waveguide are thoroughly analyzed with the modal transmission-line method and Floquet theory. The extraordinary open stopbands caused by the contra-flow coupling between a leaky parallel-plate-like waveguide and the leaky waves, which are generated by 2-D periodic structures (waveguide walls), are displayed in the form of the Brillouin diagram. The phase-match condition is used to verify the resonant coupling between the incident plane wave and the leaky parallel-plate-like waveguide modes. Specifically, the transmission peak frequencies are accurately predicted.     

一种新的简化行波边界条件在FDTD算法中的实现

本文提出一种新的边界条件。这种边界条件在边界处强加理想导体对计算场区进行截断,而将由此产生的反射场分离去除,从而减小反射所产生的干扰。与PML边界条件相比,由于它不需要吸收层,不需要PML层中人为的场量分解,因此节约了内存,提高了计算速度。文中给出一维、二维空间的计算实例,计算结果表明原理是可行的。     

近红外单/多频石墨烯谐振腔吸波器研究

采用传输矩阵法研究了石墨烯谐振腔在一维周期结构中的吸波特性。在700~950 nm波段,通过改变不同介质的尺寸、入射角大小以及电磁波模式等参数,分析了吸收频点及吸收峰值的变化情况。研究结果表明,在改变缺陷层的尺寸时,可产生单频点或双频点吸收峰;入射角及电磁波模式的变化对吸收峰的峰值影响较大。以上分析结果可以为近红外石墨烯吸波器的设计提供理论依据。     

Susceptibility analysis of wiring in a complex system combining a3-D solver and a transmission-line network simulation

This paper deals with the application of electromagnetic field-to-transmission-line coupling models for large cable systems analysis. It emphasizes the use of Agrawal's (1980) model applied here in a numerical simulation of an electromagnetic susceptibility problem up to 500 MHz. Based on the concepts of EM topology, the proposed methodology consists in calculating the incident fields with a three-dimensional (3-D) computer code and the coupling on cables with a multiconductor transmission-line network computer code. In order to validate the efficiency of this methodology in an industrial context, an experiment has been performed on a prototype wiring installed in a Renault Laguna car, stressed by an EM plane wave. Numerous validation configurations have been carried out. First, the prototype cable network under study has been tested on a ground plane to validate the coupling model but also, to validate the cable-network topology itself. Second, EM fields have been measured onto the structure and inside the structure. Then, they have been compared to 3-D calculations, performed with an FDTD code. Third, comparisons between measurements and calculations of bulk currents and voltages on 50 Ω loads on the wiring have been achieved     

A new procedure for interfacing the transmission line matrix (TLM)method with frequency-domain solutions

The authors present a new procedure that interfaces the transmission-line matrix (TLM) method with frequency-domain solutions of electromagnetic fields. Frequency-domain solutions are transformed into appropriate time-domain sequences using the discrete Fourier transform (DFT). Hence, the corresponding boundary Johns matrix can be determined with minimum computational effort. The subsequent treatment consists in convolving the streams of TLM impulses incident on the boundary with a Johns matrix generated with the new approach. The method is used to obtain the time-domain reflection sequence of wideband absorbing terminations in a rectangular waveguide in the dominant mode operation. In addition, the time-domain analysis of pulse penetration through a sheet with high, but finite, conductivity is presented. Good results demonstrate the efficiency of the proposed procedure     

The Analysis of Radial Transmission-Line in W-Band Circular Groove Guide

In this paper, finite-difference time-domain (FDTD) method is used to calculate the driving-point impedance of radial transmission-line in circular groove guide. A simple way is used to approximate the curvilinear metal boundary of circular groove guide. And perfectly matched layer (PML) is applied on the open boundary of circular groove guide. Fine-grid is used to calculate the EM fields in the radial transmission-line in which we are interest. Discretized wave equation is used to update the tangential electric field on the boundary of coarse- and fine-grid. At last, the driving-point impedances related to different diameter of the radial transmission-line are obtained from the ratio of the Fourier transform of the voltage to the Fourier transform of the current.     

Response of a planar microstrip line excited by an externalelectromagnetic field

The voltages and currents induced by external electromagnetic fields on a planar microstrip line have been studied with the use of a distributed-source transmission-line model. The frequency response of the microstrip line has been analyzed by simulating the illuminating field with a plane wave arbitrarily incident on the line. The influence of the microstrip geometrical and electrical characteristics on the voltages and currents induced on the line has been examined, and indications for reducing the circuit susceptibility have been obtained. The model adopted can be used for studying the response of the line to any type of external field arbitrarily varying in space time. Numerical results show that for lines loaded with the characteristic impedance at both terminals, voltage amplitudes on the order of some millivolts and currents of some hundreds of microamperes can be induced at f=3 GHz by an incident plane wave with an electric-field intensity of 1 V/m and for various angles of incidence. The voltages and currents induced on a microstrip circuit can be reduced by using substrates of sufficiently high permittivity     

基于正折射率材料的一维负折射率光子晶体

对一维光子晶体折射现象的研究大都基于等效折射率, 并没有考虑入射光波经过光子晶体后的光强。通过研究一维光子晶体的折射现象, 考虑入射光波经过光子晶体后的强度也是很有必要的。用传输矩阵法和 Bloch定理分析了两种正常材料构成的一维光子晶体, 当两种材料的介电常数比和填充比分别为 1.33和 0.31, 用归一化频率为 0.655的光波以 18毅角斜入射该光子晶体时, 结果显示：光波发生了负折射, 并且透过率大于 20%。     

Shunt stub line impedance matching: a wave reflection analysistutorial

This paper presents a detailed transmission-line wave reflection analysis for the situation where an antenna's feed-point impedance is matched to the transmission-line characteristic impedance through the use of a shunt stub line. In most engineering texts, the steady-state solution to the shunt-stub-line impedance-matching problem is presented in detail. However, the solution in terms of a wave reflection analysis is generally not presented, since the steady-state solution is sufficient for most practical applications. This article is presented as a tutorial review of both the steady-state solution and the solution as determined through a detailed wave reflection analysis. It is conceptually and mathematically demonstrated that the wave reflections created at the antenna and at the stub-line termination do not cancel one another at the stub-line connection point, and they do not stay separate from one another. It is demonstrated that the steady-state impedance match is achieved when the wave reflections created at the antenna and at the stub-line termination combine at the connection point to cancel the initial wave reflections created at the connection point. The analysis and resulting formulas presented are derived for the general problem of a stub line being connected in parallel to a transmission line at any point, and are therefore valid independently of an impedance match being established at the connection point. The analysis and formulas are valid for any combination of transmission-line length, transmission-line properties, antenna impedance, stub line length, and stub line termination impedance     

光子晶体微谐振腔的调谐特性

利用光学传输矩阵法研究了3种基于一维缺陷态光子晶体的微谐振腔的调谐特性。结果发现,对于每种结构,在某一波长的波垂直进入光子晶体时,在缺陷层位置会激发起幅度远大于入射波幅度的场,即产生了谐振现象并形成了微谐振腔;改变缺陷层厚度可对谐振波长调谐;对于缺陷层两侧为高折射率介质层的结构1和结构2,调谐特性呈现出非线性;而对于缺陷层两侧为低折射率介质层的结构3,调谐特性是线性的。在单模工作条件下,结构1和2的调谐范围约为结构3的3倍。